I'm leaving town until after the midterms and likely won't be able to fully follow the lead up and results. That means that this prediction is earlier than I would normally make it, and is going to miss some late developments. That said, midterms don't change on a dime...usually. THAT said, Georgia and Pennsylvania could very likely change on a dime. Also, there have been two trends to follow this summer, and that is unusual - they also go in opposite directions so the trend matters if it continues. So I'm going to give two Senate predictions: a right now one, and an if the trend continues one.
The Senate in a lot of ways comes down to a couple questions: Is 538's model better than prediction markets and what will the polling error be? Prediction markets seem to be explicitly factoring in a 3 to 4% Democrat bias in polls, which has been common lately. 538 doesn't explicitly take this into account, though their model results do favor R's more than polls, so some of that is there. At publishing time, 538 gives R's 42% chance of taking the Senate (and Nate Silver says his gut says toss-up). Predict It has R's at 65% chance and Iowa is waffling between 50/50 and very slight R favor.
The house is always a lighter prediction and I usually give myself + or - 5 on my seat number. I'll leave it at that but won't be disappointed if I'm off by a couple more. So:
The house: 247 republican seats plus or minus 5. If I miss this one, it is likely that I am too favorable for Democrats. See my Senate prediction for reasons why. I see no real plausible scenario where the D's keep the house (though it is possible - say 15% chance). If they do keep the house then my senate projection will be crap as well.
For the Senate, it comes down to 4 races. I think Ohio, North Carolina and Wisconsin are NOT in those 4. I think they are relatively safe wins for Republicans and if the R's lose any one or more of those the Senate is in Democrat hands, likely with an improved majority. I don't really see that happening but it is certainly not out of the question (say 25%). The races that will decide the balance of power are Pennsylvania, Georgia, Nevada and Arizona. If the R's lose PA they need 2 of the other three. If they hold PA, they need one. Georgia and Pennsylvania are the crazy races...two famous people competing against deeply flawed candidates.
Georgia: Warnock (the D) won in a runoff that was basically GIVEN to the D's by Trump's extremely bad strategy regarding stimulus checks (or intentionally throwing the election in a fit of temper - you just can't tell with trump). Warnock never should have stood a chance. Walker (the R) is famous, but also with a checkered past of accusations and recent abortion accusations (I won't go into those here). Adding to the intrigue, if neither candidate wins 50% we will see ANOTHER GA runoff, possibly for control of the Senate, just like in 2020. Never underestimate the R's ability to fuck up a runoff even though it is traditionally an easy win for them.
Pennsylvania: a TV shyster versus a man who recently had a stroke and won't disclose his medical records. I fully understand why he won't disclose them, since no matter what they say they will be used against him. This race highlights everything that is wrong with our two party cesspool. In a rational world, there would be a way to step back in this race and come up with a fair way of resolving these issues without the entire fate of the civilized world depending on whether a red or blue asshole wins this election.
Nevada and Arizona are much more traditional Red/Blue battles, with Nevada slightly in R favor and AZ slightly in D favor. GA and PA are classic toss-ups, both could easily be impacted by late news events, though it is important to note that voting has already started in Georgia. Lots of early votes are being cast, which I traditionally think favors D's, but I am not so sure about that in GA.
So the NOW prediction: at the end of election night, there will be 50 seats in Republican hands and 49 seats in Democrat hands with Georgia going to a runoff. Recent history says D's are favored in a GA runoff but long history says R's are favored. I think Walker and Trump will find a way to fuck up the runoff while D's will be more disciplined and on message. BUT, inflation and economy will have time to get worse and this will favor R's. At the end of the year it will be 51 R seats and 49 D seats. I have exactly ZERO confidence in my runoff prediction.
Taking the long view, the D's over the summer defied normal mid term trends with a consistent improvement in their prospects for the Senate, reaching almost 80% chances of winning Senate per 538's model. Abortion rulings, legislative success, student loan forgiveness and falling gas prices all worked in D's favor. D's played the summer almost perfectly. But they shot their ammunition too soon. Trends have steadily drifted back in R's favor, with inflation, gas prices, immigration, mortgage rates and general dissatisfaction all working in the R's favor. I don't expect any serious relief in any of those areas, and, in fact expect the trend to get worse. The attitude of the country is not likely to improve in the next couple weeks. This all favors R's. A late Supreme Court decision or other major event could scupper this, but their best chance: The Court blocking Biden's student loan forgiveness just got eliminated by Amy denying a preliminary injunction. This surprised me. So, reading the tea leaves, if trends continue as they have, I see 53 R seats and 47 D seats. Obviously I have no idea if trends continue and this is NOT how I do election predictions So....
My official prediction is the 50/49 R/D with GA runoff and R's taking the runoff.